Thread: Old MAF vs new MAF

Very nice work!

Originally Posted by OffTrack

Very nice work!

x 2!

A few questions if I may: W
. What are the units of your pressure and flow axes?
. What are the red numbers on the turbo performance charts?
Thanks,

Originally Posted by Leo109

x 2!

A few questions if I may: W
. What are the units of your pressure and flow axes?
. What are the red numbers on the turbo performance charts?
Thanks,

On the turbo pressure/flow chart the Y axis is absolute pressure RATIO, ie the ratio between manifold pressure and atmospheric pressure, this is a unitless property and providing you measure both pressures in the same units it will work out the same no matter what the units are, if you look at the spreadsheet you will see I use the atmospheric pressure which is in kPa and the boost pressure in Bar, so to get the absolute pressure ratio I need to use this formule

pressure ratio =(BOOST x 100 +ABS)/ABS

the horizontal axis it lbs/min, however, the nanocom shows the units are g/s, but they are actually kg/hr, so my sheet does a conversion from kg/hr to lbs/min

There are two sets of red numbers the percentage numbers refer to the elliptical zones and represent turbo efficiency, ideally you want to follow the dotted line which is the sweet spot of turbo performance, the arcs show the turbo rotation speed in revs/min... yes it really does spin that fast!

both the axes on the MAP/MAF comparison chart are the same units, I think they are miligramms/cylinder charge, unless you are using them for further tuning calcs the actual units are unimportant, whats critical is they are in the same units because again we are interested in the ratio.

Might sound picky, but was looking at one of my captures pasted in.
I noted that my MAP to MAF plot has almost two distinct lines in the clustering, the majority are 1.08 gradient, the second a bit steeper, but my capture was longer and during that time the IAT went from 10 to 25 degrees. I'm guessing that the ambient and manifold pressure values to air mass could do with a correction for inlet and post compression temperatures, which may resolve the lines down to a single one and potentially alter the ratios a bit.

I also plotted MAP - MAF against IAT and again got an error suggesting that temperature for IAT/MAP is adding an offset to results (MAP conversion giving a bit greater volume at the higher IAT).

Interesting though and nice to do a bit of cross correlation of the two sensors to see if they are working OK.

When importing your own data make sure that you modify the charts to include the rows you want to map.

Temperature should not be an issue, the MAF is basically a sophisticated temperature guage that compensates for differing air density due to temperature and the MAP is also the IAT sensor, if your seeing a temperature related trend then could be a fault in either of the sensors, in which case refer to the turbo chart, the one thats furthest from the sweetspot is probably the faulty one.

Its worth inspecting your nanocom data, I've found some nanocom files appear to stop recording some values

Also bear in mind your engine type, if its an EU2 engine then it used the MAP for airmass calcs and the EU3 uses the MAF.

The airmass calcs appear on the smoke limiter map in your ECU, which will limit the fuel input for a given airmass, if your airmass is measured low (ratio is below 1 on and EU3 or above 1 on an EU2), then the smoke map may be clipping your fuel delivery, on the otherhand if the airmass is measured high then you may get more smoke

The MAF does temperature compensate, however the MAP doesn't (AFAIK), that is why the sensor has both pressure and temperature sensor back to the ecu, I guess the ECU can use the inlet pressure and temperature along with the manifold pressure and temperature to calculate air mass. The manifold temperature isn't however pushed out by the nancom.

It's an EU3, which is why I was curious, the MAF values look 'right' when considering the change in temperatures for inlet and boost coming from the MAP. I guess this is why the MAF might have taken over, it's just easier to work on that sensor data than doing the PVT calcs for the before and after boosting data, I thought it was weird at first after so long with a TDi, but I guess this shows that boost pressure can be a bit of a crude tool in comparison to the MAF values.

The curves are both in bounds, but if I plotted the earlier 'cold' values I'd see one trend and if I plotted the later 'hot' values I'd see the other. I'll post the excel up after lunch

EDIT
I hadn't spotted the IAT reference in the formula, quick glance I saw 273 and assumed an estimated temperature value. This is after including my IAT values. However, I thought the IAT was the airbox value (certainly doesn't look like the manifold temperature) so there's probably still a difference, the manifold air temp will be higher due to boost IAT+BOOST_INC-IC_COOLING.
engine check sa.xlsx